Current protocol for treating DCS and the possibility of subtle signs and symptoms

[Amar]

Hi Dr Deco,
I am a medical doctor and also a keen diver. Over the last 2 years we have had 2 cases of DCS come to our hospital (strange as it is an inland hospital). After seeing the two cases it got me questioning current medical practice in treating DCS. One was an "undeserved" hit and the other one was a case of cerebral DCS after serious decompression violation.
It got me thinking that the current theory behind cerebral DCS is that a venous bubble is able to get into the arterial circulation and embolise in the brain. This is the same thing that happens in a stroke (although it is not a bubble). It is well known in the medical community that the majority of strokes are silent. This means that the person who had the stroke did not have any obvious symptoms but it was picked up incidentally on a scan. People who have had these silent strokes have been found to have cognitive decline. With this knowledge it seems reasonable to think that "silent" cerebral DCS could happen after provocative dives that could have significant effects on a divers life even though there were no obvious symptoms.
My question is that current practice is that divers with significant decompression violations are only treated if there are symptoms of DCS. is there a reason for this as it seems to me that there are people who could be having the equivalent of these silent strokes that could have a significant effect on a divers life that are not treated?

 

[Duke Dive Medicine]

Amar,

I'm sure Dr. Powell will add to this, but to get you started:

Significant decompression violations are likely to result in clinical manifestations of DCS rather than silent infarcts. Military divers and civilian commercial divers have protocols for treating omitted decompression in on-site recompression chambers, but the transport times for recreational divers are often so long as to make this impractical. For example, our facility is about three hours' drive from the nearest beach. If a diver omitted decompression on a dive and was asymptomatic but was concerned enough to have himself/herself transported to us, it would probably be a minimum of five or six hours before we saw him/her. By then, we'd have expected any DCI to declare itself. If he/she remained completely asymptomatic and a thorough neurological exam didn't reveal any deficits, we would keep him/her under observation but probably would not treat him/her. Other clinics that are closer to the beach may do things differently, though.

As part of the ELTHI diving study, UK divers and offshore oil workers were examined by MRI. These papers are linked below; unfortunately, they're just UHMS meeting abstracts so the entire paper isn't available on Rubicon:

[abstract] A COMPARISON OF WHITE MATTER HYPERINTENSITIES IN DIVERS AND OFFSHORE WORKERS USING MAGNETIC RESONANCE IMAGING (MRI): THE ELTHI DIVING STUDY
[abstract] EXAMINATION OF THE LONG TERM HEALTH IMPACT OF DIVING (THE ELTHI DIVING STUDY): RE-ANALYSIS OF CEREBRAL MRI DATA ALLOWING FOR CONFOUNDING FACTORS (re-analysis of data from the above paper)

There doesn't seem to be a lot of conclusive evidence of long-term neurological changes in divers who have not suffered from DCS as compared to non-divers.

There's also a chapter in Bennett and Elliott's Physiology and Medicine of Diving that covers the long-term effects of diving on the central nervous system if you're interested in reading further.

If you ever get a case that you have any questions about, please feel free to call us. Our contact info is on our website, linked below.

Best,
DDM

 

[boulderjohn]

With this knowledge it seems reasonable to think that "silent" cerebral DCS could happen after provocative dives that could have significant effects on a divers life even though there were no obvious symptoms.
My question is that current practice is that divers with significant decompression violations are only treated if there are symptoms of DCS. is there a reason for this as it seems to me that there are people who could be having the equivalent of these silent strokes that could have a significant effect on a divers life that are not treated?

This isn't a medical reply, but it may partially address the problems associated with treating people who do not have clear signs of DCS.

The last issue of DAN's Alert Diver had a very disturbing article about the growing difficulty of getting treatment for people with clear symptoms of DCS. Many chambers will not open for a diver, even in clear distress, unless the diver comes to them during normal business hours. Even when they do, they are often turned away if the physician on duty does not believe the symptoms are severe enough. This happened one time when I was in Ginnie Springs, FL--the Gainesville hospital turned a diver away, and he had to be transported a long distance for treatment.

So what if you have less clear symptoms?

Not long ago I had the most clear and convincing symptoms of DCS I have ever had. I awoke with shoulder and elbow pain and distinct and persistent numbness in my hands. I had other symptoms as well. The only thing that stopped me from calling DAN for a consultation was the fact that I had not been diving in three weeks. The cause was more likely related to overdoing it on the gardening and home repair work that day. I have had many, many cases in which I have had marginal symptoms of DCS that could also be related to the effects of lugging heavy dive equipment, including steel doubles, around for a weekend.

The difficulty for me is knowing when these vague symptoms cross the line and make it worthwhile for me to get some sort of treatment. I am sure I can recognize a major hit when it happens--how can I know about the lesser ones?

 

[Saturation]

I'm not DrDeco but this is a unique question I think has not been brought up before. So, I'll take a stab at it for the sake of archives and future discussions.

Prophylactic recompressions have been done prn, its the decision of the patient's attending doc. But its not a standard approach.

The status quo is since DCI is defined purely on clinical grounds, at least by the UHMS, then ipso facto an asymptomatic patient has no DCI, regardless of any violation, and doesn't necessitate treatment.

However, if a significant violation occurred, its the clinicians call to consider watchful waiting, and/or 02 supplementation and/or overnight observation. If they choose chamber treatment what is the end point of treatment and which table is justified? Recompression is >= $5000 per treatment and substantial time involved, not to mention the risk/beneift to the patient.

When we look into the cause of DCI or its proxy, bubbles, we find strong suggestion that bubble quantity and size are associated with DCI risk. Bubbling and long term effects of diving is less well studied. Thus, if patients are asymptomatic but bubble substantially post dive, suppressing bubbles provides a studied benefit by reducing risk and provides some objective and quantifiable sign of 'pre-decompression illness' or stress [ the association between bubble scores and risk of DCI is established ]. If bubbling is made part of a DCI definition, a grade can be established as the minimally acceptable diagnosis, set a threshold for mandatory treatment and finally treatment success, even without symptoms.


Long-term Effects of Sport Diving

..
My question is that current practice is that divers with significant decompression violations are only treated if there are symptoms of DCS. is there a reason for this as it seems to me that there are people who could be having the equivalent of these silent strokes that could have a significant effect on a divers life that are not treated?

 

[Duke Dive Medicine]

This isn't a medical reply, but it may partially address the problems associated with treating people who do not have clear signs of DCS.

The last issue of DAN's Alert Diver had a very disturbing article about the growing difficulty of getting treatment for people with clear symptoms of DCS. Many chambers will not open for a diver, even in clear distress, unless the diver comes to them during normal business hours. Even when they do, they are often turned away if the physician on duty does not believe the symptoms are severe enough. This happened one time when I was in Ginnie Springs, FL--the Gainesville hospital turned a diver away, and he had to be transported a long distance for treatment.

So what if you have less clear symptoms?

Not long ago I had the most clear and convincing symptoms of DCS I have ever had. I awoke with shoulder and elbow pain and distinct and persistent numbness in my hands. I had other symptoms as well. The only thing that stopped me from calling DAN for a consultation was the fact that I had not been diving in three weeks. The cause was more likely related to overdoing it on the gardening and home repair work that day. I have had many, many cases in which I have had marginal symptoms of DCS that could also be related to the effects of lugging heavy dive equipment, including steel doubles, around for a weekend.

The difficulty for me is knowing when these vague symptoms cross the line and make it worthwhile for me to get some sort of treatment. I am sure I can recognize a major hit when it happens--how can I know about the lesser ones?

John,

The Alert Diver article highlights an issue that we in the hyperbaric field have been concerned about for a long time. A lot of facilities are finding that there's no money in being on call 24-7 so they change to a working-hours-only schedule and focus on wound care, which shifts the burden of caring for emergency patients to the comparatively few chambers that will accept them. We've had carbon monoxide poisoning patients flown in from as far away as Richmond, Virginia.

Saturation mentioned that decompression illness is a clinical diagnosis, which in this context means that it's a diagnosis that's made based on observable signs and symptoms. You essentially did the same thing that a physician would do, i.e. you determined that based on your dive history and symptom onset time, your pain and numbness couldn't have been related to DCI. If the symptoms occur in the setting of a dive trip, it's best to let a qualified diving physician make that call. The differential diagnosis is based on dive profile, symptom onset time, and a thorough neurological examination. If it's unclear whether symptoms are caused by DCI or mechanical injury, a prudent physician will treat the diver in the chamber since DCI is the more potentially harmful of the two diagnoses.

Your post also reinforces the point that divers who think they have decompression illness should go to the nearest emergency department rather than presenting themselves at a hyperbaric facility and requesting treatment. For the most part, ED staff know where the closest emergency chambers in the area are. If a physician at a storefront clinic or hospital wound care center refuses to treat a diver, it's a good indication that that physician isn't comfortable with treating diving injuries, in which case the diver is arguably better off going to a facility with trained diving physicians.

Best regards,
DDM

 

[Dr Deco]

Hello Amar:

As others have written, prophylactic treatment of divers would be expensive and time prohibitive.\Even if divers operated their own chamber “on the cheap,” time is a big factor.

MRI Lesions

MRI studies have indicated white matter lesions in divers with DCS. These lesions appear both in dives with obvious problems and those without and with about the same frequency. Additionally, these lesions also appear in nondivers, also with about the same frequency. These MRI lesions appear to be an epiphenomenon to something not yet identified.

ParadoxicalStroke

Your questionis essentially concerning paradoxical stroke and bubbles. [For divers unfamiliarwith the term, this stroke-producing clot essentially originates on the venous side.] With diving, the situation is worse than with clots. Venouse-side clots can enter the systemic circulation only with a defect e.g., a PFO or ASD. Bubbles can enter through a PFO, the pulmonary circulation [in some cases], and the process is made worse when many bubbles are present and the right side pressure increases in the lung circulation.

Post-dive Bubbles

Divers vary in their propensity to produce bubbles post dive. Neurological DCS is not common and is most likely much less likely than dive bubbles – likewise copious numbers of bubbles. This is true because the dive tables would have been changed if these problems arose with much frequency. [I know because I have worked with table designers.]

Venous side bubbles do not persist for more than an hour post surfacing except in minimal numbers. Even in divers with joint-pain DCS, there are essentially no Doppler bubbles an hour later. This is also true in my experience in the laboratory with large animals such as pigs and sheep.

Severe DCS and missed decompression are a different matter – but we are talking prophylactic treatment of minor decompression flaws.

Dr Deco :doctor: